1. Field of the Invention
The present invention relates generally to a method of stabilizing the viscosity of thickened compositions. In particular, the present invention relates to a method of stabilizing the viscosity of aqueous compositions for cleaning glass, porcelain, metal, laundry, carpeting, upholstery, shampoo and air fragrancing.
2. Brief Description of the Background Art
Thickened compositions are highly desirable for a variety of consumer products such as air fragrancing compositions, laundry, liquid dishwashing detergents, shampoo, oven cleaning, upholstery and carpet cleaning. It has been observed that these thickened compositions may lose viscosity during manufacturing due, in part, to the shearing and aeration of compositions during preparation, transfer, storage and filling operations into bottles and other dispensing containers. Thus, it is important to maintain a sufficiently high viscosity prior to filling in order to achieve the desired viscosity of the finished product.
Applicant has observed that some thickened compositions also experience viscosity losses within one hour from making the composition. When the compositions were left overnight in storage vessels, the viscosity losses were significant. Smaller volumes of composition appear to be more greatly affected, potentially due to large surface area to volume relationship. For example, a 1200 ml. beaker containing 200 ml. of product having an initial viscosity of about 100 centipoise ("cps") lost approximately 40 cps after only 6 hours of storage, while a storage container containing 5000 gallons (about 18.9 kiloliters) of the same product lost approximately 10 cps after about 16 hours of storage. Attempts to compensate for this viscosity loss by increasing the levels of thickening agents in the composition have proven inadequate for certain consumer products. For example, increasing the levels of thickening agents in glass cleaners can produce undesirable streaking from the increased residue on the glass surface.